System and method of evaluating an object using electromagnetic energy

ABSTRACT

A system for evaluating subject objects includes at least one physical source operable to emit electromagnetic energy and driver electronics drivingly coupled to at least one physical source. The driver electronics is configured to drive at least one physical source as a number of logical sources, using an electromagnetic forcing function. The number of logical sources is greater than the number of physical sources. In addition, the system includes a sensor configured to receive an electromagnetic response from at least a portion of an evaluation object illuminated by one or more physical sources operated as logical sources, and convert the electromagnetic response to a test response signal indicative of the electromagnetic response of the evaluation object.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.12/375,814, filed Jan. 30, 2009, now pending, which is a U.S. nationalstage application filed under 35 U.S.C. §371 of International PatentApplication PCT/US2007/017082, accorded an international filing date ofJul. 30, 2007, which claims benefit under 35 U.S.C. 119(e) to U.S.Provisional Patent Application No. 60/820,938, filed Jul. 31, 2006, eachof which are incorporated herein, by reference, in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure generally relates to evaluation systems, and moreparticularly to systems that evaluate characteristics of an object usingelectromagnetic energy.

2. Description of the Related Art

There are a number of proposed systems that employ spectral analysis oflight received from a sample to recognize the sample.

US Patent Application Publication 2006-0161788 A1 describes full colorspectrum object authentication methods and systems. In particular, aspectrum measuring device measures a region of respective sampledobjects to produce spectral content information that identifies thesampled objects. The spectrum measuring device includes a plurality ofindividual sensors, which preferably includes specialized narrow bandnear-infrared and near-ultraviolet sensors, for example photodiodes orphotomultipliers. Computers employ spectral analysis software togenerate a unique measured pattern, which is then compared withreference patterns stored in a database. The spectral analysis softwaremay be remotely located on a server accessible by the computers. Thespectral analysis is preferably performed using XYZ color spacemodeling, although other color space models may be employed. The regionbeing sampled may be varied to prevent third parties from easilyanticipating the location. Samples may be taken from multiple regions toinsure accuracy.

U.S. Pat. No. 5,844,680 is directed to a device and process formeasuring and analyzing spectral radiation, in particular for measuringand analyzing color characteristics. In particular, a number ofradiation sources are provided in combination with a sensor fordetecting radiation within a desired wavelength range. The radiationsources have spectral characteristics that are linearly independent fromone another, but overlap so that in combination, the radiation sourcesgenerate radiation over the entire desired wavelength range.Alternatively, a single radiation source is provided that generatesradiation over the entire desired wavelength range, in combination witha plurality of sensors that have spectral sensing characteristics thatare linearly independent from one another, but overlap the entiredesired wavelength range. A control unit stores a number of calibrationfunctions with linearly independent spectral characteristics.

The patents and other publications directed to the field of objectauthentication and/or object identification are too numerous todescribe. The above described publication and patent are onlyrepresentative.

BRIEF SUMMARY

It may be useful to determine whether an object being evaluated isidentical to a previously evaluated object; in other words determinewhether an object being sampled is the exact same object as a referenceobject. Alternatively, it may be useful to determine whether an objectbeing evaluated is similar to a reference object; in other wordsdetermine whether an object being sampled is a facsimile of thereference object. In order to uniquely identify a large number ofobjects, it may be useful to capture a large number of distinctreference responses from one or more reference objects. This may bedifficult to do with fixed illumination. This may also be difficult todo when sensing at a limited number of bands. It may also be useful toseparate hardware and/or software functions into separate systems thatmay be remote to one another. Such may reduce costs and/or permit theuse of hardware or software that could not otherwise be financiallyjustified. It may also be useful to apply the object evaluation tospecific applications, for example: manufacturing process control,quality assurance, media authentication, biological tissue recognition,identification, verification, authentication, classification, and/ordiagnostics.

In one aspect, a system for evaluating subject objects includes at leastone physical source operable to emit electromagnetic energy and driverelectronics drivingly coupled to the at least one physical source. Thedriver electronics is configured to drive at least one physical sourceas a number of logical sources, using an electromagnetic forcingfunction. At least some of the logical sources have emission spectradifferent than emission spectra of other logical sources. The number oflogical sources is greater than the number of physical sources. Inaddition, the system includes a sensor configured to receive anelectromagnetic response from at least a portion of an evaluation objectilluminated by one or more physical sources operated as logical sources,and convert the electromagnetic response to a test response signalindicative of the electromagnetic response of the evaluation object.

In another aspect, a method for evaluating an evaluation object withrespect to at least one reference object includes driving at least onephysical source of a plurality of physical sources with anelectromagnetic forcing function, where each of at least some of thephysical sources are driven as a plurality of logical sources.Additionally, the method includes receiving an electromagnetic responsefrom at least a portion of an illuminated region of the evaluationobject, converting the electromagnetic response to a test responsesignal indicative of the response of the illuminated portion of theevaluation object, and comparing the test response signal correspondingto the evaluation object with a reference response signal indicative ofa response of at least one reference object to illumination byelectromagnetic energy.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn, are notintended to convey any information regarding the actual shape of theparticular elements, and have been solely selected for ease ofrecognition in the drawings.

FIG. 1 is a schematic diagram showing an object evaluation system,according to one embodiment.

FIG. 2 is an end view showing a transducer unit of the object testdevice illustrated in FIG. 1, according to one illustrated embodiment.

FIG. 3 is a cross-sectional diagram showing an A-A′ cross-section of thetransducer unit illustrated in FIG. 2, according to one illustratedembodiment.

FIGS. 4A-4C are graphs illustrating a portion of an exemplaryelectromagnetic forcing function that drives physical sources of thetransducer unit as a plurality of logical sources, according to oneillustrated embodiment.

FIG. 5 is a cross-sectional diagram showing an A-A′ cross-section of thetransducer unit illustrated in FIG. 2, according to another illustratedembodiment.

FIG. 6 is a cross-sectional diagram showing an A-A′ cross-section of thetransducer unit illustrated in FIG. 2, according to a furtherillustrated embodiment.

FIG. 7 is a graph illustrating an exemplary test response signalindicative of an electromagnetic response from an evaluation objectilluminated by physical sources being driven in a user-selected sequencewhile being rotated at a given angular velocity for two differentelevation angles, according to another illustrated embodiment.

FIGS. 8A-8C are schematic diagrams illustrating the driving of thephysical sources through three cycles of a user-selected sequence as asource mount assembly and the physical sources rotate through 360degrees, according to one illustrated embodiment.

FIG. 9A is a cross-sectional diagram showing an A-A′ cross-section ofthe transducer unit illustrated in FIG. 2, according to one illustratedembodiment.

FIG. 9B is an end view of the transducer unit illustrated in

FIG. 9A.

FIG. 9C is a cross-sectional diagram showing an A-A′ cross-section ofthe transducer unit illustrated in FIG. 2, according to anotherillustrated embodiment.

FIG. 10 is a flow chart showing a method of evaluating an object by theobject test device illustrated in FIG. 1, according to one illustratedembodiment.

FIG. 11 is a flow chart showing a method of generating referenceresponse signals indicative of electromagnetic responses of referenceobjects to illumination by electromagnetic energy, according to oneillustrated embodiment.

FIGS. 12-14 are schematic diagrams showing construction of an exemplaryreference response signal, according to one illustrated embodiment.

FIG. 15 is a flow chart showing a method of constructing referenceresponse signals indicative of an electromagnetic response of referenceobjects to illumination by electromagnetic energy supplied by physicalsources being driven as N logical sources, according to anotherillustrated embodiment.

FIG. 16 is a flow chart showing a method of constructing a reflectancefunction of the evaluation object to evaluate the evaluation objectagainst reference objects, according to one illustrated embodiment.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures associated with computing systems,networks, servers, microprocessors, memories, buses, and sources ofelectromagnetic energy have not been shown or described in detail toavoid unnecessarily obscuring descriptions of the embodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense, that is as “including, but not limited to.” Referencethroughout this specification to “one embodiment” or “an embodiment”means that a particular feature, structure or characteristic describedin connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment. Further more, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

The ability to recognize, identify, verify, authenticate and/or classifyobjects has numerous commercial applications.

It may be useful in some applications to determine whether an objectbeing evaluated is identical to a previously evaluated object; in otherwords determine whether an object being sampled is the exact same objectas a reference object. Alternatively, it may be useful to determinewhether an object being evaluated is similar to a reference object; inother words determine whether an object being sampled is a facsimile ofthe reference object.

For example, it may be useful to determine whether a manufactured objectis identical to, or has the same spectral characteristics of apreviously evaluated manufactured object. Such may be useful inauthenticating goods, and deterring counterfeiting or gray marketing ofgoods. Such may also be useful in manufacturing process control and/orquality control. Also for example, it may also be useful to determinewhether other objects, such as paintings or other works of art areidentical to a previously sampled work of art.

For example, it may be useful to determine whether a medium is identicalor has the same spectral characteristics as a previously evaluatedmedium. Such may be useful to determine whether a medium such as adocument identical or similar to a previously evaluated document. Suchmay be useful in recognizing, identifying, verifying, authenticatingand/or classifying financial instruments such as currency, checks,bonds, money orders, securities, credit cards, debit cards, and/or giftcards. Such may also be useful in recognizing, identifying, verifying,authenticating and/or classifying identification documents, such aspassports, identity cards (e.g., national, state, provincial, military,employer, school, organization), driver's licenses, and/or birth ornaturalization certificates. Such may also be useful in recognizing,identifying, verifying, authenticating and/or classifying legaldocuments such as licenses, permits, assignments, deeds, wills,declarations, oaths, agreements, pleadings, or motions. Such may beuseful in recognizing, identifying, verifying, authenticating and/orclassifying medical related documents, such as medical records, medicaldata, medical reports, and/or medical images (e.g., X-Ray, CAT scan,MRI, tomography, etc.). Such may be useful in deterring fraud and/ormisuse of documents and other media.

Also for example, it may be useful to determine whether a piece ofbiological tissue from a subject is the same or similar to a previouslyevaluated piece of tissue, based on spectral characteristics. Such maybe useful in recognizing, identifying, verifying, authenticating,classifying, and/or diagnosing biological tissue or the subject fromwhich the tissue is derived. Bodily tissue may for example includeretinal tissue, skin, blood, bone, hair, organs, etc.

It may be particular useful where the above may occur based on thenatural conditions or attributes of the object, media, or biologicaltissue, without the need to apply dedicated indicia such as serialnumbers, machine-readable symbols (e.g., barcode symbols, area or matrixcode symbols, stack code symbols), and/or radio frequency identification(RFID tags.) Such dedicated data carriers may, in some embodiments,provide additional information regarding the object.

All of the above may, or may not employ additional information about theobject to facilitate the process. Additional information may include oneor more measurable or observable physical characteristics of the object,media or biological tissue, for example, height, weight, age, hair oreye color, gender, location, type, size, denomination, serial numbers,security features, name, type, serial numbers, date of issue, color,etc. Such additional information may be employed to confirm a match, orto reduce the number of reference responses for comparison with a testresponse.

The ability to perform such in a network environment may provide avariety of distinct advantages. For example, such may make possible lowcost end user test devices, which share or gain remote access to highercost computing hardware and software. Such may allow the costs of thecomputing hardware and software to be shared over a variety of end usersor financial entities. Such may also allow for “centralization” ofrelatively higher cost computing hardware and software, perhapspermitting use of high speed super-computers that could not otherwise befinancially justified for individual end users or small groups of endusers. Such also may allow for “decentralization” of low cost samplingor test device. Such may also allow for light weight and/or low powerconsuming test devices. Such may additionally or alternatively permitthe upgrade of previously distributed test devices. Such may also permitthe distribution of work load. Such may also facilitate the backing upof data, and provide for redundancy. Other advantages will be apparentfrom the teachings herein.

FIG. 1 shows an object evaluation system 100 according to one embodimentof the invention.

The object evaluation system 100 includes an object test device 102, acomputer system 104, and a database 106. The object test device 102includes a control unit 108 and a transducer unit 110. The control unit108 includes driver electronics 111 and signal processing electronics112. The computer system 104 may take any of a variety of forms, forexample, personal computers, mini-computers, work stations, or mainframe computers. The computer system 104 may, for example, take the formof a server computer executing server software. Computer system 104 iswell known in the art, and may include a computing device 107, memory,input/output devices, and peripherals. The computing device 107 may be amicroprocessor, a central processing unit (CPU), or a virtual devicerunning on the CPU, for example. The memory may include volatile andnonvolatile memory, such as RAM and ROM, and/or include other forms ofmass storage devices, including one or more hard disks or RAID drives,CD/ROMs, or other mass storage devices.

In another embodiment, the control unit 108 of the object test device102 includes the computer system 104. For example, the control unit 108may include the computing device 107 (e.g., a microprocessor) andmemory, as well as user-operable switches and/or a keypad with anelectronic display.

The memory may store evaluation software executable by themicroprocessor for operating the object test device 102. A user mayprogram the evaluation software to control the object test device 102.In another embodiment, the object test device 102 includes the database106.

As illustrated in FIG. 1, the object test device 102 is communicativelycoupled to the computer system 104 via a first communication cable 114.The first communication cable 114 enables the computer system 104 tosend and receive data, control, and power signals to the object testdevice 102. Additionally, the computer system 104 is communicativelycoupled to the database 106 via a second communication cable 115. Inanother embodiment, the object test device 102, the computer system 104and the database 106, or any combination thereof, may be configured tosupport wireless communication of data, control and power signals.Additionally, or alternatively, the object test device 102, computersystem 104 and/or database 106 may be communicatively coupled by one ormore networks (not shown). The network can take a variety of forms, forexample one or more local area networks (LANs), wide area networks(WANs), wireless LANs (WLANs), and/or wireless WANs (WWANs). The network16 a may employ packet switching or any other type of transmissionprotocol. The network may, for example, take the form of the Internet orWorldwide Web portion of the Internet. The network may take the form ofpublic switched telephone network (PSTN) or any combination of theabove, or other networks.

FIG. 2 is an end view of the transducer unit 110 of the object testdevice 102 illustrated in FIG. 1.

The transducer unit 110 includes a sensor 116 and N physical sources 118a-118 j (collectively 118), where N is a positive integer. For ease ofillustration, FIG. 2 shows ten physical sources (i.e., N=10), howeverany number of physical sources may be employed. The physical sources 118a-118 j emit electromagnetic energy. Each source of the physical sources118 a-118 j may emit electromagnetic energy in a respective band of theelectromagnetic spectrum. If the physical sources 118 a-118 j are drivenat the same power level by the driver electronics 111, then in oneembodiment, each physical source of the physical sources 118 a-118 j hasan emission spectrum that is different from the emission spectra of theother physical sources 118 a-118 j. In another embodiment, at least onephysical source of the physical sources 118 a-118 j has an emissionspectrum that is different from the emission spectra of the otherphysical sources 118 a-118 j. In one embodiment, the physical sources118 a-118 j are light emitting diodes (LEDS). In yet another embodiment,the physical sources 118 a-118 j are tunable lasers. Alternatively, oradditionally, the physical sources 118 a-118 j may take the form of oneor more incandescent sources such as conventional or halogen lightbulbs. Alternatively, or additionally, the sources 44 may take the formof one or more organic LEDs (OLEDs, also referred to in the relevant artas “electronic paper”), which may advantageously be formed on a flexiblesubstrate. Alternatively, or additionally, the physical sources 118a-118 j may, for example, take the form of one or more sources ofmicrowave, radio wave or X-ray electromagnetic energy.

One, more or all of the physical sources 118 a-118 j may be operable toemit in part or all of an “optical” portion of the electromagneticspectrum, including the (human) visible portion, near infrared portionand/or or near ultraviolet portions of the electromagnetic spectrum.Additionally, or alternatively, the physical sources 118 a-118 j may beoperable to emit electromagnetic energy other portions of theelectromagnetic spectrum, for example the infrared, ultraviolet and/ormicrowave portions.

In some embodiments, at least some of the physical sources 118 areoperable to emit in or at a different band than other of the physicalsources 118. For example, one or more physical sources 118 may emit in aband centered around 450 nm, while one or more of the physical sources118 may emit in a band centered around 500 nm, while a further source orsources emit in a band centered around 550 nm. In some embodiments, eachphysical source 118 emits in a band centered around a respectivefrequency or wavelength, different than each of the other physicalsources 118. Using physical sources 118 with different band centersadvantageously maximizes the number of distinct samples that may becaptured from a fixed number of physical sources 118. This may beparticularly advantageous where the test device 102 is relatively small,and has limited space or footprint for the sources 44.

Further, the spectral content for each of the physical sources 118 mayvary according to a drive level (e.g., current, voltage, duty cycle),temperature, and other environmental factors. Thus, the emission spectraof each of the sources 118 may have at least one of a different center,bandwidth and/or other more complex differences in spectral content,such as those described above (e.g., width of the band, the skew of thedistribution, the kurtosis, etc.) from those of the other sources 118.Such variation may be advantageously actively employed to operate one ormore of the physical sources 118 as a plurality of “logical sources,”each of the logical sources operable to provide a respective emissionspectra from a respective physical source 118. Thus, for example, thecenter of the band of emission for LEDs may vary according to drivecurrent and/or temperature. One way the spectral content can vary isthat the peak wavelength can shift. However, the width of the band, theskew of the distribution, the kurtosis, etc., can also vary. Suchvariations may be also be advantageously employed to operate thephysical sources 118 as a plurality of logical sources. Thus, even ifthe peak wavelength were to remain constant, the changes in bandwidth,skew, kurtosis, and any other change in the spectrum can provide usefulvariations in the operation of the object test device 112. Likewise, thecenter of the band of emission may be varied for tunable lasers. Varyingthe center of emission bands for one or more physical sources 118advantageously maximizes the number of samples that may be captured froma fixed number of physical sources 118. Again, this may be particularlyadvantageous where the test device 102 is relatively small, and haslimited space or footprint for the physical sources 118.

A field of emission of one or more physical sources 118 may be movablewith respect to a housing. For example, one or more physical sources 118may be movable mounted with respect to the housing, such as mounted fortranslation along one or more axes, and/or mounted for rotation oroscillation about one or more axes. Alternatively, or additionally, thetest device 102 may include one or more elements operable to deflect orotherwise position the emitted electromagnetic energy. The elements may,for example, include one or more optical elements, for example lensassemblies, mirrors, prisms, diffraction gratings, etc. For example, theoptical elements may include an oscillating mirror, rotating polygonalmirror or prism, or MEMS micro-mirror that oscillates about one or moreaxes. The elements may, for example, include one or more other elements,example permanent magnets or electromagnets such as those associatedwith cathode ray tubes and/or mass spectrometers. Structures for movingthe field of emission and the operation of such are discussed in moredetail below.

The sensor 116 can take a variety of forms suitable for sensing orresponding to electromagnetic energy. For example, the sensor 116 maytake the form of one or more photodiodes (e.g., germanium photodiodes,silicon photodiodes). Alternatively, or additionally, the sensor 116 maytake the form of one or more CMOS image sensors. Alternatively, oradditionally, the sensor 116 may take the form of one or more chargecouple devices (CCDs). Alternatively, or additionally the sensor 116 maytake the form of one or more micro-channel plates. Other forms ofelectromagnetic sensors may be employed, which are suitable to detectthe wavelengths expected to be returned in response to the particularillumination and properties of the object being illuminated.

The sensor 116 may be formed as individual elements, one-dimensionalarray of elements and/or two-dimensional array of elements. For example,the sensor 116 may be formed by one germanium photodiode and one siliconphotodiode, each having differing spectral sensitivities. For example,the object test device 112 may employ a number of photodiodes withidentical spectral sensitivities, with different colored filters (e.g.,gel filters, dichroic filters, thin-film filters, etc) over thephotodiodes to change their spectral sensitivity. This may provide asimple, low-cost approach for creating a set of sensors with differentspectral sensitivities, particularly since germanium photodiodes arecurrently significantly more expensive that silicon photodiodes.Alternatively, or additionally, the sensor 116 may take the form of oneor more photomultiplier tubes. For example, the sensor 116 may be formedfrom one CCD array (one-dimensional or two-dimensional) and one or morephotodiodes (e.g., germanium photodiodes and/or silicon photodiodes).For example, the sensor 116 may be formed as a one- or two-dimensionalarray of photodiodes. A two-dimensional array of photodiodes enablesvery fast capture rate (i.e., camera speed) and may be particular suitedto use is assembly lines or high speed sorting operations. For example,the sensor 116 may be formed as a one- or two-dimensional array ofphotomultipliers. Combinations of the above elements may also beemployed.

In some embodiments, the sensor 116 may be a broadband sensor sensitiveor responsive over a broad band of wavelengths of electromagneticenergy. In some embodiments, the sensor 116 may be a narrowband sensorsensitive or responsive over a narrow band of wavelengths ofelectromagnetic energy. In some embodiments, the sensor 116 may take theform of several sensor elements, as least some of the sensor elementssensitive or responsive to one narrow band of wavelengths, while othersensor elements are sensitive or responsive to a different narrow bandof wavelengths. This approach may advantageously increase the number ofsamples that may be acquired using a fixed number of sources. In suchembodiments the narrow bands may, or may not, overlap.

In some embodiments, the source 118 may also serve as the sensor 116.For example, an LED may be operated to emit electromagnetic energy atone time, and detect returned electromagnetic energy at another time.For example, the LED may be switched from operating as a source tooperating as a detector by reverse biasing the LED. Also for example, anLED may be operated to emit electromagnetic energy at one time, anddetect returned electromagnetic energy at the same time, for example byforward biasing the LED.

A field of view of the sensor 116 or one or more elements of the sensor116 may be movable with respect to the housing. For example, one or moreelements of the sensor 116 may be movably mounted with respect to thehousing, such as mounted for translation along one or more axes, and/ormounted for rotation or oscillation about one or more axes.Alternatively, or additionally, the test device 102 may include one ormore elements operable to deflect or otherwise position the returnedelectromagnetic energy. The elements may, for example, include one ormore optical elements, for example lens assemblies, mirrors, prisms,diffraction gratings, etc. For example, the optical elements may includean oscillating mirror, rotating polygonal mirror or prism, or MEMSmicro-mirror that oscillates about one or more axes. The elements may,for example, include one or more other elements, example permanentmagnets or electromagnets such as those associated with cathode raytubes and/or mass spectrometers.

In some embodiments, the source 118 may also serve as the sensor 116.For example, an LED may be operated to emit electromagnetic energy atone time, and detect returned electromagnetic energy at another time.Also for example, an LED may be operated to emit electromagnetic energyat one time, and detect returned electromagnetic energy at the sametime.

The physical sources 118 a-118 j are mounted on a source end plate 120and the sensor 116 is mounted on a sensor end plate 122. In anotherembodiment, the source and sensor end plates 120 and 122, respectively,form a contiguous plate. As illustrated, the physical sources 118 a-118j are mounted on the source end plate 120 to form a circle, with thesensor 116 mounted along an axis 124 that is normal to the source endplate 120 and which passes approximately through a center of the circle.The sensor 116 may be located at any position along the axis 124, aswill be discussed further below with reference to FIG. 3.

In operation, a user may instruct the computer system 104 via theevaluation software to drive the physical sources 118 a-118 j in aselected sequence with an electromagnetic forcing function. A physicalsource emits electromagnetic energy when driven by the electromagneticforcing function. In one embodiment, the computer system 104 drives thephysical sources 118 a-118 j via the driver electronics 111. The driverelectronics 111 may include any combination of switches, transistors andmultiplexers, as known by one of skill in the art or later developed, todrive the physical sources 118 a-118 j in a selected drive pattern.

The electromagnetic forcing function may be a current, a voltage and/orduty cycle. In one embodiment, a forcing function is a variable currentthat drives one or more of the physical sources 118 a-118 j in theselected drive pattern (also referred to as a selected sequence). In oneembodiment, the computer system 104 drives the physical sources 118a-118 j (or any subset of the physical sources 118 a-118 j) in theselected sequence, in which only one or zero physical sources are beingdriven at any given instant of time. In another embodiment, the computersystem 104 drives two or more physical sources of the physical sources118 a-118 j at the same time for an overlapping time period during theselected sequence. The computer system 104 may operate automatically, ormay be responsive to user input from a user. Use of the electromagneticforcing function to drive the physical sources 118 a-118 j as a numberof logical sources is discussed further below with reference to FIG. 4.

FIG. 3 shows the transducer unit 110 according to one illustratedembodiment.

The transducer unit 110 may be placed proximate a surface 126 of anevaluation object 128 that is the subject of evaluation. The evaluationobject 128 includes objects that reflect, refract, transmit, fluoresce,phosphoresce and/or absorb and re-radiate or otherwise return incidentelectromagnetic energy. The evaluation object 128 may be in any state ofmatter, including solid, liquid or gaseous states. Each physical sourceof the physical sources 118 a-118 j, when driven, illuminates a portion130 of the surface 126 of the evaluation object 128. As used herein andin the claims, the terms illuminate, illuminates, illumination, andvariations of such terms mean to expose to or reveal by the use ofelectromagnetic energy or electromagnetic radiation, whether in thevisible portion of the electromagnetic spectrum, the optical portion(e.g., visible, near-infrared, near-ultraviolet), or other portions(e.g., far-infrared, far-ultraviolet, microwave, X-ray, etc.).

Typically, the evaluation object 128 reflects, emits, fluoresces orotherwise returns an electromagnetic response to the illumination. Thespectral content of the electromagnetic response depends upon thespectrum of the electromagnetic energy incident upon the evaluationobject 128 and upon the physical, chemical and electrical properties ofthe evaluation object 128. Some or all of the electromagnetic responseis incident upon the sensor 116.

For example, as illustrated in FIG. 3, driver electronics 111 drivesphysical source 118 h via a user-adjustable electromagnetic forcingfunction to emit electromagnetic energy. The electromagnetic energyemitted by physical source 118 h illuminates a portion 130 of thesurface 126 of the evaluation object 128. Based in part upon the contourof the surface 126 and the electrical and chemical properties of theobject 128, an electromagnetic response from some or all of theilluminated portion 130 of the surface 126 is received by the sensor116. For example, an electromagnetic response received by the sensor 116may be composed of electromagnetic energy emitted from points A and B ofthe surface 126, comprising reflected and/or re-radiated or otherwisereturned light. Other points on the surface 126 may only returnelectromagnetic energy incident from the physical source 118 h. Forexample, point C only returns electromagnetic energy incident from thephysical source 118 h. The returned electromagnetic energy from pointsA, B and C is incident upon the sensor 116. For illustrative ease, onlythree points A, B and C on the surface 126 are shown to contribute tothe electromagnetic response, but many other portions of the surface 126may also contribute to the response.

FIGS. 4A-4C illustrate a portion of an electromagnetic forcing function132 that drives the physical sources 118 a-118 j as a plurality oflogical sources, according to one illustrated embodiment.

In this embodiment, the electromagnetic forcing function 132 is a timevarying current with a saw-tooth pattern. The electromagnetic forcingfunction 132 comprises a plurality of segments 134 a-134 d (collectively134). For ease of illustration, FIG. 4A illustrates four segments 134a-134 d, however, any suitable number of segments may be employed. Inoperation, each segment 134 of the electromagnetic forcing function 132drives one physical source of the physical sources 118 a-118 j as anumber of logical sources. According to one embodiment, the number oflogical sources is greater than the number of physical sources 118 a-118j. Logical sources will be discussed further below with reference toFIG. 4B.

As an exemplary embodiment, segment 134 a drives physical source 118 a,segment 134 b drives physical source 118 b, segment 134 c drivesphysical source 118 c and segment 134 d drives physical source 118 d. Auser may instruct the computer system 104 to drive any number of thephysical sources 118 a-118 j in a selected sequence. A user may programthe selected sequence via the evaluation software, where the evaluationsoftware may be stored in the memory of the computer system 104. Themicroprocessor executes the evaluation software programmed by the userand controls the driver electronics 111 in driving the physical sources118 a-118 j by the electromagnetic forcing function 132 in the selectedsequence.

For example, a user or computer system 104 may select to drive thephysical sources 118 a-118 j in a spatially uniform sequence in whichthe physical sources 118 a-118 j are driven in an order in which theyare mounted on the source end plate 120 (e.g., {118 a, 118 b, 118 c, . .. , 118 i, 118 j}), or in a spatially non-uniform sequence, such as {118a, 118 d, 118 j, 118 i, 118 e, 118 c, 118 b, 118 g, 118 h, 118 f}.Typically, the selected sequence is repeated until the user or computersystem 104 selects a different sequence or the object test device 102 ispowered OFF. In another embodiment, the user or computer system 104 mayselect a subset of the physical sources 118 a-118 j to be driven in aselected sequence.

As discussed above, the sequence defines an order of activation for thesources 118, and may optionally define a sequence of drive levels forrespective ones of the sources 118 within the sequence. In someembodiments, the sequence can be varied periodically. In otherembodiments, the sequence may be varied randomly. In furtherembodiments, the sequence may be varied with each iteration. In stillother embodiments, the sequence may be varied based on a time and/ordate. Varying the sequence produces an inherent encryption of thesignals indicative of the test responses and/or the results. Thevariation makes it difficult for someone to determine or fake testresponses for a given object since the test response varies based on theparticular illumination sequence employed. This may be particularlyadvantageous were security is a concern, for example where identitydocuments are being authenticated, where financial instruments are beingauthenticated or where goods are being authenticated to detectforgeries. Thus, the sequence may be varied randomly, periodically,based on time and/or date, or on demand. This inherent variation may bebolstered by more conventional encryption, for example public/privatekey encryption, for example RSA encryption. Thus, the test response maybe encrypted using conventional encryption techniques. Additionally, oralternatively, the sequence may be encrypted using conventionalencryption techniques. Additionally, or alternatively, if the sequenceis transmitted, it may be transmitted separately from the test results,reducing the likelihood of interception of both. It should be noted thateven if both the sequence and resulting test response were intercepted,such information would have limited value since the sequence would orcould soon be changed.

Additionally, FIG. 4A illustrates a response signal 136 generated by thesensor 116 upon receiving an electromagnetic response emitted by theevaluation object 128 in response to illumination by the physicalsources 118 a-118 j (or a subset of the physical sources 118 a-118 j)being driven in the selected sequence by the electromagnetic forcingfunction 132. In one embodiment, the test response signal 136 is anelectrical signal 136. As illustrated, the signal processing electronics112 (FIG. 1) samples the test response signal 136 at a predeterminedsampling rate, as indicated by sampling points 138 a, 140 a, 142 a, . .. , 152 a.

According to one embodiment, the electromagnetic forcing function 132drives each physical source 118 as a plurality of logical sources. Thatis, a physical source 118 may be considered to be composed of aplurality of logical sources, where each logical source of a givenphysical source has a respective emission spectrum based upon a value ofthe electromagnetic forcing function 132 driving the given physicalsource 118 and upon optical characteristics of the given physical source118. For example, since the test response signal 136 is sampled fourtimes as a given physical source 118 is being driven, the given physicalsource 118 operates as four logical sources, where each logical sourcehas a respective emission spectrum or band, different from the emissionspectrum or band of the other logical sources for that particularphysical source 118. That is, the number of logical sources depends uponthe electromagnetic forcing function 132 and the sampling rate of thetest response signal 136.

FIG. 4B illustrates four emission spectra 154, 156, 158 and 160 of fourlogical sources corresponding to the physical source 118 a being drivenby the forcing function 132 at points 138 b, 140 b, 142 b, and 144 b,and four emission spectra 162, 164, 166 and 168 of four logical sourcescorresponding to the physical source 118 b being driven by the forcingfunction 132 at points 146 b, 148 b, 150 b, and 152 b. As illustrated,some emission spectra of the emission spectra 154-168 of the logicalsources overlap, however, in an alternate embodiment none of theemission spectra 154-168 overlap with any other of the emission spectra154-168.

FIG. 4C illustrates a composite emission spectrum 170 for physicalsource 118 a and a composite emission spectrum 172 for physical source118 b. The composite emission spectrum for any given physical source isa summation of the emission spectra of the logical sources for the givenphysical source. Thus, composite emission spectrum 170 is a summation ofthe emission spectra 154, 156, 158 and 160 corresponding to the fourlogical sources generated by driving the physical source 118 a at points138 b, 140 b, 142 b and 146 b of the forcing function 132, and compositeemission spectrum 172 is a summation of the emission spectra 162, 164,166 and 168 corresponding to the four logical sources generated bydriving the physical source 118 b at points 146 b, 148 b, 150 b and 152b of the forcing function 132. As illustrated, the composite emissionspectra of the physical sources 118 a and 118 b overlap one another in aregion Y. However, any combination of overlapping and non-overlappingcomposite emission spectra corresponding to the selected sequence ofphysical sources being driven may be employed.

FIG. 5 shows the transducer unit 110 according to another illustratedembodiment.

The transducer unit 110 includes a focusing device 174 and an aperture176. However, in other embodiments, the transducer unit 110 may includeonly the focusing device 174 or only the aperture 176. In thisembodiment, the sensor 116 is a detector array having detectors 178. Inoperation, each physical source of the physical sources 118 a-118 jdriven in a selected sequence emits electromagnetic energy toward theportion 130 of the surface 126 of the evaluation object 128. Eachdetector of the detectors 178 receives an electromagnetic responsereturned from a respective portion of the illuminated portion 130 of theevaluation object 128. For example, when physical source 118 h isdriven, the focusing device 174 focuses an electromagnetic responsereturned from a respective region 180 of the illuminated portion 130onto a detector 178 a and an electromagnetic response from a respectiveregion 182 of the illuminated portion 130 onto a detector 178 b. Whenphysical source 118 c is driven, the focusing device 174 focuses adifferent electromagnetic response from the respective region 180 of theilluminated portion 130 onto the detector 178 a.

Each detector (collectively 178) converts an electromagnetic responsecharacteristic of a respective region of the illuminated portion 130 ofthe evaluation object 128 into a signal characteristic of the respectiveregion. If the sensor 116 includes M detectors 178, then M signals areproduced. The signals may be stored in the database 106 (FIG. 1) forfurther analysis. The focusing device 174 and the aperture 176 allow fora highly reliable evaluation of the evaluation object 128 against knownreference objects, since each detector generates a signal that isindicative of an electromagnetic response for a respective sub-portion(i.e., region) of the portion 130. In contrast, the signal generated bythe sensor 116 (FIG. 3) is indicative of an electromagnetic response forthe portion 130. That is, the signal generated by the sensor 116 is aweighted average of the signals generated by the detectors 178.

FIG. 6 shows the transducer unit 110 according to still anotherillustrated embodiment.

The transducer unit 110 includes a source mount assembly 184 to whichthe physical sources 118 a-118 j are mounted. In one embodiment, thesource mount assembly 184 is moveable with respect to the evaluationobject 128. In another embodiment, the source mount assembly 184 ismoveable with respect to the evaluation object 128 and the sensor 116.

As illustrated in FIG. 6, the source mount assembly 184 is rotatable ata user-defined angular velocity w about an axis 186, where the axis 186is perpendicular to a surface 188 of the source mount assembly 184 towhich the physical sources 118 a-118 j are mounted. The source mountassembly 184 may also be pivotable by a user-defined elevation angle θabout an axis 190, where the axis 190 is perpendicular to the axis 186.

When any given physical source of the physical sources 118 a-118 j emitselectromagnetic energy, an angle of incidence of the electromagneticenergy at a given point on the surface 126 of the evaluation object 128depends upon the elevation angle θ. As illustrated, when the elevationangle θ is zero, φ₁ is the angle of incidence of electromagnetic energy(represented by a ray 192) at a point P on the surface 126. However,when the elevation angle θ is greater than zero, then φ₂ is the angle ofincidence of electromagnetic energy (represented by a ray 194) at thepoint P on the surface 126. Thus, an electromagnetic response may beobtained by driving the physical sources 118 a-118 j in a selectedsequence for a number of different elevation angles θ to illuminate theevaluation object 128.

In an exemplary embodiment, the evaluation object 128 is illuminated bydriving the physical sources 118 a-118 j in the selected sequence for afirst elevation angle (e.g., θ=0°), driving the physical sources 118a-118 j in the selected sequence for a second elevation angle (e.g.,θ=10°), and then driving the physical sources 118 a-118 j in theselected sequence for a third elevation angle (e.g., θ=20°). Theilluminated object 128 emits an electromagnetic response, a portion ofwhich is detected by the sensor 116. The sensor 116 produces a signalindicative of the electromagnetic response. For a given sampling rate,the signal contains three times more data as compared to a signalobtained by driving the physical sources 118 a-118 j in the selectedsequence at only the first elevation angle.

Additionally, the source mount assembly 184 and the physical sources 118a-118 j may rotate at a user-defined angular velocity w about the axis186. As discussed further below with reference to FIG. 7, driving thephysical sources 118 a-118 j in a selected sequence while rotating thephysical sources 118 a-118 j at an angular velocity w increases theamount of data contained in the response signal produced by the sensor116 for a given sampling rate.

FIG. 7 illustrates a test response signal 198 indicative of anelectromagnetic response from the evaluation object 128 (FIG. 6)illuminated by physical sources 118 a-118 j being driven in auser-selected sequence while being rotated at a given angular velocity wfor two different elevation angles θ, according to one exemplaryembodiment. For a first elevation angle θ=0°, the physical sources 118a-118 j are driven though one cycle of the user-selected sequence as thesource mount assembly 184 and the physical sources 118 a-118 j rotatethrough a first 120 degrees, as illustrated in FIG. 8A. In response todetection of an electromagnetic response returned by the evaluationobject 128, the sensor 116 generates a first portion 196 of the testresponse signal 198. Then the physical sources 118 a-118 j are driventhough another cycle of the user-selected sequence as the source mountassembly and the physical sources 118 a-118 j rotate through a second120 degrees, as illustrated in FIG. 8B. In response to detection of theelectromagnetic response returned by the evaluation object 128, thesensor 116 generates a second portion 200 of the test response signal198. The physical sources 118 a-118 j are then driven though anothercycle of the user-selected sequence as the source mount assembly and thephysical sources 118 a-118 j rotate through a third 120 degrees, asillustrated in FIG. 8C. In response to detection of the electromagneticresponse returned by the evaluation object 128, the sensor 116 generatesa third portion 202 of the test response signal 198.

For a second elevation angle θ=10°, for example, the physical sources118 a-118 j are driven though three more cycles of the user-selectedsequence as the source mount assembly 184 and the physical sources 118a-118 j rotate through another 360°, and thereby generating a fourthportion 204 of the test response signal 198. For a given sampling rate,the test response signal 198 comprising portions 196, 200, 202 and 204contains six times more data as compared to a test response signalobtained by driving the physical sources 118 a-118 j in the selectedsequence at only one elevation angle θ with zero angular velocity w.

FIG. 9A shows the transducer unit 110 according to a further illustratedembodiment.

The transducer unit 110 includes an electromagnetic energy directionalassembly 205 having a base portion 206 and a circumferential portion208. The directional assembly 204 modifies an angle of incidence ofelectromagnetic energy emitted by a physical source incident at a givenpoint on the surface 126. In one embodiment, the directional assembly204 is a concave lens.

As an exemplary embodiment, electromagnetic energy emitted by physicalsource 118 h and refracted by the directional assembly 205 (andrepresented by ray 210) is incident at a point Q on the surface 126 ofthe evaluation object 128 at an angle φ₂. However, with the directionalassembly 205 removed from the transducer unit 110, electromagneticenergy (represented by ray 212) emitted by physical source 118 h isincident at the point Q on the surface 126 of the evaluation object 128at an angle φ₁. Thus, the directional assembly 205 modifies the angle ofincidence from φ₁ to φ₂, thereby modifying the electromagnetic responseof the point Q to the incident electromagnetic energy and subsequentlymodifying the signal produced by the sensor 116 in response to receivingthe electromagnetic response returned by the evaluation object 128.

FIG. 9B shows the transducer unit 110 according to still a furtherillustrated embodiment.

The circumferential portion 208 of the directional assembly 205 has anindex of refraction that depends upon an angular position α. In oneembodiment, a surface of the directional assembly 205 varies as afunction of the angular position α to vary an effective index ofrefraction of the directional assembly 205 as a function of the angularposition α. For example, a surface 214 (FIG. 9A) has a different shape(e.g., a different concavity) than a surface 216. In another embodiment,an index of refraction of the concave lens 205 depends upon a lenscomposition that varies as a function of the angular position α. Inanother embodiment, the directional assembly 205 rotates about an axis218 (FIG. 9B) with a user-selected angular velocity.

FIG. 9C shows the transducer unit 110 according to yet a furtherillustrated embodiment.

As illustrated, the electromagnetic energy directional assembly 205 is arotatable mirror. When physical source 118 h is driven, electromagneticenergy (represented by ray 220) is directly transmitted at an angle ofincidence φ₁ to a point P on the surface 126 of the evaluation object128, and electromagnetic energy (represented by ray 222) is transmittedat an angle of incidence φ₂ to the point P via reflection by therotatable mirror 205.

In one embodiment, the mirror 205 is rotatable about a circumferentialaxis 224 (FIGS. 9B and 9C). For example, in operation, the physicalsources 118-118 j are driven through one or more cycles of a selectedsequence while a mirror elevation angle β is incrementally modifiedabout the circumferential axis 224.

FIG. 10 is a flow chart showing a method of evaluating an evaluationobject 128 by the object test device 102, according to one embodiment.

The method starts at 225. At 226, a user drives the physical sources 118a-118 j in a selected sequence with an electromagnetic forcing function132 to emit electromagnetic energy toward the evaluation object 128. Anynumber of the physical sources 118 a-118 j may be driven in any orderwhich may include driving any number of the physical sources 118 a-118 jfor overlapping periods of time. In one embodiment, the electromagneticforcing function 132 is configured to drive a physical source 118 as anumber of logical sources, where at least some of the logical sourceshave different emission spectra than other of the logical sources.

In one embodiment, the object test device 102 includes a computingdevice 107, memory and evaluation software (not shown). The user mayprogram the object test device 102 to drive any number of the physicalsources 118 a-118 j in the selected sequence. The selected sequence maybe stored in the memory. The microprocessor may later retrieve theselected sequence from the memory when evaluating a test signalindicative of an evaluation object against reference signals indicativeof reference objects. In one embodiment, the reference signals areelectrical reference response signals.

In another embodiment, the computer system 104 (having a microprocessorand memory) automatically selects a sequence to drive any number of thephysical sources 118 a-118 j. The selection may be based, for example,on a time of day, day of the week, or a random number generated byrandom number generator (RNG) software stored in memory and executed bythe microprocessor. RNG software is commercially available.

At 230, the sensor 116 receives an electromagnetic response returnedfrom the evaluation object 128. A spectral content of theelectromagnetic response is based upon the optical properties of theevaluation object 128, the emission spectra of the logical sources andthe electromagnetic forcing function 132. The shape (in time) of theelectromagnetic response depends additionally upon the sequence selectedfor driving the physical sources 118 a-118 j. At 232, the sensor 116converts the electromagnetic response to a signal. The signal is basedupon the spectral sensitivity and the gain of the sensor 116. The signalis indicative of the electromagnetic response of the evaluation object128 to illumination by the selected sequence of physical sources 118a-118 j driven as a number of logical sources.

At 234, the microprocessor (not shown) normalizes the signal usingnormalization factors and the computer-generated or user-selectedphysical source sequence. When the physical sources 118 a-118 j areLEDs, the spectral distribution and intensity of the spectral componentsof the logical sources for each physical source may depend upon ambientoperating temperature and variations in processing steps and materialcomposition in the manufacture of the physical sources 118 a-118 j.Thus, the database 106 may store normalization or calibration factors.The calibration may be based on a variety of factors or parameters. Forexample, the calibration may be based on a batch number in themanufacture of the physical sources 118 a-118 j, for example, and/orupon the ambient operating temperature of the physical sources 118 a-118j when being driven by the electromagnetic forcing function 132. As iswell known to one of skill in the art, the optical characteristics ofelectromagnetic energy emitted by LEDs may depend upon other factors aswell. All normalization or calibration factors that normalize theoptical characteristics of electromagnetic energy emitted by lightemitting diodes or other types of physical sources or the sensor 116 maybe employed in various embodiments. For example, variations betweendifferent manufactures, different batches of physical sources 118 by thesame manufacturer, or even between individual physical sources 118 inthe same manufacturing batch may be accommodated.

At 236, the microprocessor, using the selected physical source drivingsequence, compares the normalized test signal to reference signalsstored in the database 106. The reference signals are indicative ofelectromagnetic responses to illumination of reference objects withelectromagnetic energy. By comparing the normalized test signal to thereference signals, the microprocessor evaluates the evaluation object128 against the reference objects. In one embodiment, the microprocessormay rank the likelihood of the evaluation object 128 being identical to,or a copy of, one or more of the reference objects. The microprocessormay produce an indication of a confidence level in the match. Theconfidence level may be represented in a variety of ways, for example asa percentage of discrepancies detected or how many standard deviationsthe match is from being an identical match. Alternatively, theconfidence level may indicate the number of times a match with athreshold was found. For example, if a match was found in response tomore than one sequence, at more than one location, and/or at more thanone viewpoint or angle.

In another embodiment, the microprocessor samples the normalized testsignal at a predefined sampling rate and compares the sampled testsignal to the reference signals. In yet embodiment, the microprocessorevaluates the evaluation object 128 against the reference objects bycomputing a root-mean-squared (RMS) value for each sampled test signalcompared to a reference signal. The method terminates at 235.

FIG. 11 is a flow chart showing a method of generating referenceresponse signals indicative of electromagnetic responses of referenceobjects to illumination by electromagnetic energy, according to oneillustrated embodiment.

The method starts at 237. At 238, a microprocessor (not shown) ofcomputer system 104 drives the physical sources 118 a-118 j in auser-selected or automated computer-selected sequence with anelectromagnetic forcing function 132 to illuminate the reference object128 with electromagnetic energy. The physical sources 118 a-118 j aredriven as a plurality of logical sources. The selected sequence includesdriving any number of the physical sources 118 a-118 j in any order. Themicroprocessor drives the physical sources 118 a-118 j such that theelectromagnetic response from the illuminated reference object 128includes a plurality of segments, where each segment is an responsecorresponding to illumination of the reference object 128 by a givenphysical source of the physical sources 118 a-118 j.

At 240, the sensor 116 receives the electromagnetic response returned bythe reference object 128. The spectral content of the electromagneticresponse is based upon the optical properties of the reference object128, the emission spectra of the plurality of logical sources and theelectromagnetic forcing function 132. At 242, the sensor 116 convertsthe electromagnetic response to a reference signal. The reference signalis additionally based upon the spectral sensitivity and the gain of thesensor 116. The reference signal is indicative of the electromagneticresponse returned by the reference object in response to the sequence ofillumination.

At 243, the microprocessor normalizes the reference response signalusing normalization factors and the computer-selected or user-selectedsource driving sequence. At 244, the microprocessor stores the referencesignal and the associated source driving sequence in the database 106.The microprocessor may also store identifying characteristics or otherinformation about the reference object 128.

At 246, the user or computer system 104 decides whether to generateanother reference signal by illuminating and evaluating anotherreference object with the object test device 102. If, at 246, the userdecides to generate another reference signal, the method continues at238. Otherwise, the method ends at 247.

FIGS. 12-14 illustrate construction of a reference response signal,according to another illustrated embodiment.

In order to construct a reference response signal indicative of aresponse to illumination of a reference object by the physical sources118 a-118 j being driven as a plurality of logical sources by anelectromagnetic forcing function, a broadband spectral response 248 ofthe reference object (also referred to as a white light spectralresponse) is stored in the memory (not shown) of the computer system 104or in the database 106. In one embodiment, the broadband spectralresponse 248 of a reference object of a given material composition orwith a particular surface color coating is obtained from a third partyvendor or from the manufacturer of the reference object. For example, apaint manufacturer may know the spectral content of an electromagneticresponse produced by illuminating a particular paint with either a whitelight source or a plurality of sources having overlapping emissionspectra that collectively cover a large portion of the electromagneticspectrum from the far UV to the far IR, for example.

The microprocessor (not shown) of the computer system 104 computes aspectral response 250 corresponding to illumination of the referenceobject with a logical source having an emission spectrum 252. In oneembodiment, the spectral response 250 is the product of the emissionspectrum 252 of the logical source with the broadband spectral response248. However, one of skill in the art will appreciate other methods forcomputing the spectral response 250 of the reference object toillumination with a logical source having the emission spectrum 252.

The microprocessor computes a point P of a signal 254 based upon asensitivity and gain of the sensor 116 and the spectral response 250.Methods for computing data points of an electrical response of adetector to input signals having known spectral distributions are wellknown in the art.

FIG. 15 is a flow chart showing a method of constructing a referencesignal indicative of an electromagnetic response of a reference objectto illumination by electromagnetic energy supplied by physical sources118 a-118 j being driven as N logical sources, according to anotherillustrated embodiment.

At 256, the broadband spectral response 248 of the reference object 128is stored in the memory (not shown) of the computer system 104 or in thedatabase 106.

At 258, the microprocessor (not shown) of the computer system 104computes the spectral response 250 corresponding to illumination of thereference object 128 by a logical source having an emission spectrum252. At 260, the microprocessor computes the point P of a responsesignal 254 based upon a sensitivity and gain of the sensor 116 and thespectral response 250.

At 262, the microprocessor determines whether spectral responsescorresponding to illumination of the reference object 128 by N logicalsources have been computed. If not, then the method continues at 258,and at 260 the microprocessor computes another point of the signal 254.Acts 258-260 are repeated until N points of the signal 254 have beendetermined, where each point represents illumination of the referenceobject by one logical source of the N logical sources.

In another embodiment, the computer system 104 is configured toconstruct a reflectance function (also referred to as a reflectance or areflectivity) of the evaluation object 128 based upon response signals(e.g., electrical signals) received from the sensor 116. The testresponse signals are indicative of an electromagnetic response of theevaluation object 128 to illumination by a selected sequence of physicalsources 118 driven as a plurality of logical sources. In the discussionthat follows, the sensor 116 comprises one or more detector elements(e.g., photomultipliers).

A j^(th) logical source of the plurality of logical sources is definedto have a spectral emittance function I_(j)(f). That is, the j^(th)logical source produces electromagnetic energy of intensity p=I_(j)(f)at any given frequency f. Additionally, a k^(th) detector element of thesensor 116 is characterized by a detector response function m_(k)(f)that gives the k^(th) element's sensitivity to electromagnetic energy ofa given frequency f. Furthermore, let c_(jk)(f)=I_(j)(f) m_(k)(f), wherec_(jk)(f) is a composite function of the j_(th) logical source and thek_(th) detector element. Defining r(f) to be the reflectance of theevaluation object 128, the projection of the reflectance function r(f)on the c_(jk)(f) composite function is the inner product of thereflectance function r(f) with the composite function c_(jk)(f) (i.e.,<c_(jk)(f),r(f)>=∫I_(j)(f) m_(k)(f) r(f)df). The inner product<c_(jk)(f),r(f)> is the test response signal produced by the kthdetector element when the k^(th) detector element receives anelectromagnetic response from the evaluation object 128 beingilluminated by the j^(th) logical source. Assuming that the set offunctions C ={c_(jk)(f)} are linearly independent (i.e.,<c_(jk),c_(mn)>=0 when (j≠m, k≠n), (j=m, k≠n) or (j≠m, k=n)), then thereflectance function r(f)=Σ_(jk){<c_(jk),r>/∥c_(jk)∥}, where∥c_(jk)∥=√(<c_(jk),c_(jk)>)=√(∫c_(jk)(f)c_(jk)(f)df).

Linear independent composite functions c_(jk)(f) may be constructed inseveral ways. In one embodiment, the plurality of physical sources 118and the forcing function 132 are selected such that plurality of logicalsources are linearly independent (i.e., <I_(h)(f),I_(n)(f)>=0 for h≠n,where I_(h)(f) is the spectral emittance function of the h^(th) logicalsource) and the detectors of the sensor 116 are linearly independent(<m_(h)(f),m_(h)(f)>=0, for h≠n). In this embodiment, the compositefunctions c_(jk) built from products of linearly independent logicalsources and linearly independent detector elements are also linearlyindependent.

When the logical sources and/or detector elements are not linearlyindependent, a set of linearly independent composite functions c_(jk)may still be formed, according to another embodiment. By way of example,suppose that the transducer unit 110 includes one or two physicalsources 118 being driven as three logical sources having spectralemittance functions I₁(f), I₂(f) and I₃(f). Also suppose that the sensor116 includes two detector elements characterized by detector responsefunctions m₁(f) and m₂(f). Additionally, assume that a frequency domainF comprised of four disjoint frequency sub-domains F₁, F₂, F₃ and F₄exist in which the logical sources and the detector elements areconfigured to operate. That is, assume that I₁(f)=1 when f is a memberof F₁ U F₂ and I₁(f)=0 otherwise, I₂(f)=1 when f is a member of F₃ U F₄and I₂(f)=0 otherwise, I₃(f)=1, m₁(f)=0 when f is a member of F₄ andm₁(f)=1 otherwise, and m₂(f)=0 when f is a member of F₁ and m₂(f)=1otherwise.

Thus, one orthogonal basis set of composite functions c_(jk) comprisesC={c_(jk)}={I₂m₁, I₃m₁, I₁m₂, I₃m₂}. That is, no element of the basisset may be written as a linearly combination of the remaining elementsof the basis set. Other orthogonal basis sets may be determined. Forexample, C′={I₁m₁, I₃m₁, I₂m₂, I₃m₂} comprises elements that defineanother orthogonal basis set. One of skill in the art will appreciatethat many orthogonal basis sets comprised of linearly independentcomposite functions c_(jk) may be determined and subsequently used toconstruct the reflectance function r(f). The basis set chosen may bebased upon minimizing errors in the construction of the reflectancefunction r(f).

FIG. 16 is a flow chart showing a method of constructing a reflectancefunction of the evaluation object 128 to evaluate the evaluation object128 against reference objects, according to one embodiment.

At 264, a user, the computer system 104 or a manufacturer of the objecttest device 102, determines an orthogonal basis set C={c_(jk)(f)} ofcomposite functions c_(jk)(f). A composite function c_(jk) of the set Cis the product of the spectral emittance function of the j^(th) logicalsource with the spectral sensitivity of the k^(th) detector element ofthe sensor 116. The j^(th) logical source is one logical source of theplurality of logical sources generated as the physical sources 118 aredriven in a selected sequence by an electromagnetic forcing function.The composite functions are linearly independent if <c_(jk),c_(mn)>=0when (j≠m, k≠n), (j=m, k≠n) or (j≠m, k=n). The number of basis functionsc_(jk) required to span the composite function frequency space (i.e.,the dimensionality of the frequency space) is equal to the product ofthe dimensionality of the logical source space and the dimensionality ofthe detector element space. One of skill in the art will appreciate thatthere exist many ways to construct an orthogonal basis set C={c_(jk)(f)}of composite functions c_(jk)(f).

At 266, the composite functions are normalized and stored in a memory ofthe computer system 104 or in the database 106. For example, given acomposite function c_(jk)(f)=I_(j)(f)m_(k)(f), a normalized compositefunction ∥c_(jk)(f)∥=√(<c_(jk),c_(jk)>)=√(∫c_(jk)(f)c_(jk)(f)df).

At 268, a computing device (e.g., a microprocessor) of the computersystem 104 determines the reflectance function of the evaluation object128 based upon the test response signal produced by the detectors of thesensor 116 and the normalized composite functions ∥c_(jk)(f)∥ when thephysical sources 118 are driven as a number of logical sources toilluminate the evaluation object 128 in a selected sequence.Specifically, the reflectance function r(f)=Σ_(jk){<c_(jk),r>/∥c_(jk)∥},where <c_(jk),r>=∫I_(j)(f) m_(k)(f) r(f)df). That is, <c_(jk),r> is thetest response signal produced by the k^(th) detector element of thesensor 116 when the object evaluation 128 is illuminated by the j^(th)logical source. As an exemplary embodiment, assume that the physicalsources 118 comprise three logical sources in which only two of thethree logical sources are linearly independent, and the sensor 116comprises two linearly independent detector elements. Based upon thefrequency space occupied by the three logical sources I₁(f), I₂(f),I₃(f) and the two detector elements m₁(f) m₂(f), four linearlyindependent composite functions c_(jk) may be constructed. In oneembodiment, C={c_(jk)}={I₂m₁, I₃m₁, I₁m₂, I₃m₂}. Other sets comprisingfour different linearly independent composite functions may also beconstructed. A reflectance function of the evaluation object may beconstructed based upon a test response signal produced by detectorelement m₂ when the object is illuminated by logical source I₁, a signalproduced by detector element m₁ when the object is illuminated bylogical source I₂, and test response signals produced by detectorelements m₁ and m₂ when the object is illuminated by logical source I₃.

At step 270, the microprocessor evaluates the evaluation object bycomparing the reflectance function r(f) determined for the evaluationobject 128 to reference reflectance functions stored in the database 106or in the memory of the computer system 104. In one embodiment, thereference reflectance functions are obtained from the manufacturer(s) ofthe reference objects or from third party sources, for example. Bycomparing the reflectance function to the reference reflectancefunctions, the microprocessor evaluates the evaluation object 128against the reference objects.

EXAMPLES Example 1 ID/Passport Verification

A pattern database of passport photos of every U.S. citizen may besearchable within seconds to confirm their identity. For securitypurposes, the search patterns for the entire database may be changed,for example, in less than thirty minutes or even on demand. This mayreduce or eliminate identification document fraud, and also reduces oreliminates the cracking the security code.

The object evaluation system 100 can verify a passport or otheridentification documentation as follows:

When a passport application is submitted, a photo is included which willbe affixed to a validly issued passport. The photo identifies the personsubmitting the application. Once the issuing authority determines that apassport is to be issued, the issuing authority will generate and storeat least one known reference pattern associated with the photo (thereference object in this example), as well as other identity informationrelating to the identity of the person to whom the passport is issued,such as the person's name, physical characteristics, address, socialsecurity number, etc. (other issuance information can also be includedif necessary, such as for example the date of issuance). A data filecontaining the reference pattern and associated identity information isstored in the data structure with a plurality of other referencepatterns generated by the issuing authority for other validly issuedpassports. The issued passport containing the photo is then sent to theperson who submitted the application.

At a security checkpoint, for example at an airport terminal, a passportis provided by a traveler for identification purposes. The passport(sampled object) is provided to the object test device 102 of the system100. A region is selected within the passport photo (the sampled object128 in this example) for which a spectrum measuring device of the objecttest device 102 measures the spectral contents, i.e., color information,and outputs information indicative of the same to the computer system104 or microprocessor operating spatial analysis software.

The spectral content information outputted by the spectrum measuringdevice is provided as input to the spatial analysis software program,which generates a measured pattern for the sampled passport photo. Insome embodiments, the measured pattern may be in the XYZ color space,and/or the measured pattern can be observed from virtually any angle.The measure pattern (or a view key generated therefrom) is compared tothe plurality of reference patterns stored in the passport issuingauthority's database (or view keys generated therefrom) until a matchingreference pattern is found. If a matching reference pattern is notfound, then the passport is deemed to be a fraud by the spatial analysissoftware. If a match is located, identity information associated withthe matching reference pattern is analyzed to determine if the identityinformation for the matching reference pattern substantially correspondsto the identity information associated with the sampled passport photo.

At least a portion of the identity information associated with thesampled passport photo is generally located within the passport, and canbe provided to the spatial analysis software for analysis (e.g., by theuser entering or scanning the identity information present in thepassport), and/or the identity information within the passport can beprovided to the human user to perform the comparison. If the identityinformation associated with the sampled passport photo matches theidentity information associated with the matching reference pattern, thepassport photo will be deemed an authentic and validly issued passport(i.e., not a forgery) by the spatial analysis software, and the travelerwill be permitted to proceed past the security checkpoint.

Further, it should be understood that the materials used to constructthe passport (or other identification documentation materials) can bevalidated against known spectral or color data. The paper and inks canbe checked to determine if the passport itself is a forgery, not justthe photo or information printed on the document.

Example 2 Document Authentication

The object evaluation system 100 can be used to detect forgeries of adocument of value, such as money or bank notes, or other sensitivedocuments operates as follows:

When a document is validly produced, the producing entity generates andstores at least one reference pattern for the original document (thereference object in this example), as well as other identity informationrelating to the identity or characteristics of the document, such as thedate it was produced, a general title for the document, key terms ormonetary value, etc. A data structure containing the reference patternand identity information associated with the reference pattern is thendelivered or made available to an eligible recipient of the originaldocument.

When the recipient is later presented with a document (sampled object128), the recipient can use the object evaluation system 100 to checkthe authenticity of the presented document, i.e., to determine whetherthe presented document is the original document or of the same qualityor origin as the original document. It should be understood that if thedocument is one that is duplicated, such as a dollar bill for example,then only reference patterns for one representative document needs to beused for authentication.

The presented document is provided to a spectrum measuring device of theobject test device 102. A region is selected within the presenteddocument (the sampled object 128 in this example) for which the spectrummeasuring device measures the spectral content and outputs informationindicative of the same to the computing system 104 or microprocessoroperating spatial analysis software.

The spectral content information outputted by the spectrum measuringdevice is provided as input to the spatial analysis software, whichgenerates a measured pattern for the sampled document. The measuredpattern (or a view key generated therefrom) is compared to the specificreference pattern previously generated for the original document (or aview key generated therefrom). If the measured pattern does not matchthe reference pattern, then the presented document is deemed a forgeryby the spectral analysis software. If the measured pattern matches thereference pattern, then the presented document is deemed authentic bythe spectral analysis software and the recipient can accept thepresented document.

For further authentication, the identity information associated with theoriginal document can also be compared to identity informationassociated with the presented document to determine if theysubstantially correspond. At least a portion of the identity informationassociated with the presented document is generally located within thedocument, and can be provided to the spatial analysis software foranalysis (e.g., by the user entering or scanning the identityinformation present in the document), and/or the identity informationwithin the presented document can be provided to the human user toperform the comparison.

Example 3 Product Monitoring

The object evaluation system 100 can be used for brand protection toverify the authenticity of a product based on the make of its material(e.g., fabric colors) operates as follows:

When a manufacturer mass produces a product, at least one referencepattern for a representative of the product (the reference object inthis example) is generated and stored in the reference pattern datastructure, as well as identity information associated with the originalproduct, such as the name or style of the product, a serial number, acolor description, a size, the manufacturer's name and address, etc.

To determine if the product (sampled object 128) is of the same qualityor of the same origin as the original representative product, adistributor or individual consumer can provide the product to be sampledto the object evaluation system 100. A region is selected within thesampled product (the sampled object 128 in this example) for which aspectrum measuring device of the object test device 102 measures thespectral content and outputs information indicative of the same to thecomputer system 104 or microprocessor operating spatial analysissoftware.

The spectral content information outputted by the spectrum measuringdevice is provided as input to the computer system 104 or microprocessorexecuting the spatial analysis software, which generates a measuredpattern for the sampled product 128. The measured pattern (or a view keygenerated therefrom) is compared to the reference patterns in the datastructure (or view keys generated therefrom) until a matching referencepattern is found. If a matching reference pattern is not found, then thesampled product 128 is deemed to be a fraud. If a match is located, thenthe identity information associated with the matching reference patternis analyzed to determine if the identity information for the matchingreference pattern substantially corresponds to the identity informationassociated with the sampled product. At least a portion of the identityinformation associated with the sampled product 128 is generally locatedon a label or tag on the product, or observable by a human user, and canbe provided to the computer system 104 or microprocessor executing thespatial analysis software for analysis (e.g., by the user entering orscanning the identity information present in the label or tag orobtained from observation), and/or the identity information associatedwith the matching reference pattern can be provided to the human user toperform the comparison. If the identity information associated with thesampled product 128 matches the identity information associated with thematching reference pattern, the sampled product 128 will be deemedauthentic and the purchase and/or distribution of the sampled product128 can proceed. If the measured pattern does not match the referencepattern, then the sampled product 128 is deemed a knock-off or tamperedproduct.

Thus, the object evaluation system 100 can be utilized for brandprotection to verify the authenticity of products based on the make oftheir fabric colors with the pattern of the original product indatabase, the system 100 can compare a knock off versus the real productin a matter of minutes by scanning any area of the product for which adatabase pattern exists. In a preferred embodiment, once the fabric hasbeen scanned, a view key is selected to obtain a pattern file. Thispattern file will be compared against a pattern from an authentic fabricsample on our database from the same view key point.

Art forgery is anther area of product verification that the objectevaluation system 100 can be used. That is, spectral data can be takenfrom one or more regions of a valuable piece of art and this spectraldata could be used to authenticate copies or unknown works.

Quality Control of Manufacturing Process

The object evaluation system 100 can be also be used for quality controlof manufacturing processes to maintain quality control on practicallyany manufactured good or the packaging for the good. In this regard, thesystem 100 would operate as follows:

When a manufacturer mass produces a product, a variety of referencepatterns can be taken from the product (reference object) at differentlocations or areas within the manufacturing process. To determine if themanufacturing process is operating properly, readings can be taken fromthe products (sampled objects 128) during actual manufacturing andcompared to the reference patterns to determine whether themanufacturing process is operating to predetermined quality controlstandards. Depending upon the results of the comparison, themanufacturing process can be shut down or modified (if the comparisonshows unacceptable quality control) or subsequent parts of themanufacturing process can be actuated. For example, if the product(sampled object 128) was a loaf of bread being baked within an oven,then readings could be taken of the loaf of bread and compared with thereference patterns until the comparisons indicate the loaf of bread isready to be removed from the oven.

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to other systems for recognizing,identifying, verifying, authenticating, classifying, and/or diagnosingor otherwise evaluating objects such as, but not limited to,manufactured goods and articles; media, for example identity documents,financial instruments, legal documents, other documents and other media;and biological tissue, not necessarily the exemplary networkedevaluation system generally described above.

The foregoing detailed description has set forth various embodiments ofthe devices and/or processes via the use of block diagrams, schematics,and examples. Insofar as such block diagrams, schematics, and examplescontain one or more functions and/or operations, it will be understoodby those skilled in the art that each function and/or operation withinsuch block diagrams, flowcharts, or examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or virtually any combination thereof. In one embodiment, thepresent subject matter may be implemented via Application SpecificIntegrated Circuits (ASICs). However, those skilled in the art willrecognize that the embodiments disclosed herein, in whole or in part,can be equivalently implemented in standard integrated circuits, as oneor more computer programs running on one or more computers (e.g., as oneor more programs running on one or more computer systems), as one ormore programs running on one or more controllers (e.g.,microcontrollers) as one or more programs running on one or moreprocessors (e.g., microprocessors), as firmware, or as virtually anycombination thereof, and that designing the circuitry and/or writing thecode for the software and or firmware would be well within the skill ofone of ordinary skill in the art in light of this disclosure. The systemmay, for example include one or more analog to digital converters (ADCs)and/or one or more digital to analog converters (DACs). An ADC may, forexample, be used for converting analog photodiode responses into digitaldata for further analysis and/or transmission. A DAC may, for example,be used for converting digital computer commands into analog LED currentlevels.

In addition, those skilled in the art will appreciate that themechanisms of taught herein are capable of being distributed as aprogram product in a variety of forms, and that an illustrativeembodiment applies equally regardless of the particular type of signalbearing media used to actually carry out the distribution. Examples ofsignal bearing media include, but are not limited to, the following:recordable type media such as floppy disks, hard disk drives, CD ROMs,digital tape, and computer memory; and transmission type media such asdigital and analog communication links using TDM or IP basedcommunication links (e.g., packet links).

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet, including butnot limited to: U.S. provisional patent application Ser. Nos.60/623,881, filed Nov. 1, 2004; 60/732,163, filed Oct. 31, 2005;60/820,938, filed Jul. 31, 2006; 60/834,662, filed Jul. 31, 2006; and60/834,589, filed Jul. 31, 2006; 60/871,639, filed Dec. 22, 2006;60/883,312, filed Jan. 3, 2007; and 60/890,446, filed Feb. 16, 2007; andU.S. nonprovisional patent application Ser. No. 11/264,626, filed Nov.1, 2005, are incorporated herein by reference, in their entirety.Aspects of the embodiments can be modified, if necessary, to employsystems, circuits and concepts of the various patents, applications andpublications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A system, comprising: a computer-readable medium that stores adatabase including a plurality of reference patterns, the referencepatterns indicative of a broadband electromagnetic response by at leasta first reference object, at least two of the reference patternsindicative of respective broadband responses to illumination of thefirst reference object by at least one physical source with respectiveones of at least two different bands of electromagnetic energy.
 2. Thesystem of claim 1 wherein the respective ones of the at least twodifferent bands of electromagnetic energy partially overlap one another.3. The system of claim 1 wherein the database includes sourcenormalization values for each of a plurality of physical sources.
 4. Thesystem of claim 3, further comprising: a computing device coupled to thedatabase, the computing device configured to: receive a test responsesignal indicative of an electromagnetic response to illumination of anevaluation object being evaluated by the at least one physical source;normalize the test response signal based upon the stored sourcenormalization values; and compare the normalized test response signal toat least one of the stored plurality of reference patterns to evaluatethe evaluation object.
 5. The system of claim 3 wherein thenormalization values depend upon an ambient operating temperature of theat least one physical source.